/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.rest.messages;

import java.util.ArrayList;
import java.util.List;

/**
 * This class represents query parameters of a request. For example, the URL "/jobs?state=running" has a
 * "state" query parameter, with "running" being its value string representation.
 *
 * <p>Query parameters may both occur multiple times or be of the form "key=value1,value2,value3". If a query parameter
 * is specified multiple times the individual values are concatenated with {@code ,} and passed as a single value to
 * {@link #convertToString(List)}.
 */
public abstract class MessageQueryParameter<X> extends MessageParameter<List<X>> {
	protected MessageQueryParameter(String key, MessageParameterRequisiteness requisiteness) {
		super(key, requisiteness);
	}

	@Override
	public List<X> convertFromString(String values) throws ConversionException {
		String[] splitValues = values.split(",");
		List<X> list = new ArrayList<>();
		for (String value : splitValues) {
			list.add(convertStringToValue(value));
		}
		return list;
	}

	/**
	 * Converts the given string to a valid value of this parameter.
	 *
	 * @param value string representation of parameter value
	 * @return parameter value
	 */
	public abstract X convertStringToValue(String value) throws ConversionException;

	@Override
	public String convertToString(List<X> values) {
		StringBuilder sb = new StringBuilder();
		boolean first = true;
		for (X value : values) {
			if (first) {
				sb.append(convertValueToString(value));
				first = false;
			} else {
				sb.append(",");
				sb.append(convertValueToString(value));
			}
		}
		return sb.toString();
	}

	/**
	 * Converts the given value to its string representation.
	 *
	 * @param value parameter value
	 * @return string representation of typed value
	 */
	public abstract String convertValueToString(X value);
}
